The present invention relates to contactor health and more specifically to a system and method that can be customized by a user for predicting the health of contactors and the remaining life of contactors.
Contactors are generally used in motor starter applications to switch on/off a load as well as to protect a load, such as a motor, or other electrical devices, from current overloading. As such, a typical contactor has one or more contact assemblies—a contact assembly for each phase or pole required for the electrical device. Each contact assembly, in turn, includes a pair of stationary contacts and a pair of moveable contacts. One stationary contact will be a line side contact and the other stationary contact will be a load side contact. The moveable contacts are controlled by an actuating assembly comprising a contact carrier and an armature magnet assembly which is energized by a coil to move the moveable contacts to form a bridge between the stationary contacts. When the moveable contacts are engaged with both stationary contacts, current is allowed to travel from the power source or line to the load or electrical device. When the moveable contact is separated from the stationary contacts, an open circuit is created and the line and load are electrically isolated from one another.
Since contactors and motor starters are important components of both automation and control systems, monitoring their remaining useable life, or “health”, to predict impending faults before occurrence is essential. Un-predicted failures of contactors not only cause costly work stoppages, but also can cause damage to a load and other related systems and equipment. In contrast, over-cautious approaches to contactor monitoring and replacement increase maintenance costs and slow or delay usage of the motor/load.
Currently, most methods for estimating the working life of contactors rely upon the manufacturer's life test data or guidelines. That is, most commercially available contactors have a designated number of operations or cycles (e.g., 100,000 to 2,500,000 operations) after which the manufacturer recommends replacement to avoid failure in use. Thus, many systems and methods for predicting failure simply count the number of operations that a contactor completes. However, each contactor will not necessarily operate for the same number of cycles before failure. Exacerbating matters, the causes of failures vary among contactors as well as the conditions which lead to possible failure issues. How a contactor is operated, the conditions under which a contactor is used, and the characteristics of the environment in which a contactor is used cause even more variation in the number of operations a contactor might undergo before failure. Therefore, to be useful, counting methods must be overly cautious in setting replacement schedules, or risk contactor failures while in use. In addition, some types of loads, or one time events such as faults, can drastically change the expected life of a contactor which reinforces the usefullness of a real time monitoring system such as the one proposed in this ‘User Customizable Contactor Prognostics System’.
In addition, different applications have different consequences when contactors fail. For this reason, the conditions under which contactors should be replaced may vary between applications. For example, in the case of an auto manufacturer, a failed contactor may result in severe and expensive damage to manufacturing robots while a failed contactor in a transfer line associated with a machine vision system may simply mean that a part is not imaged properly and no physical damage may result. Here, the auto manufacturer would likely have a lower tolerance for contactor failure than the manufacturer employing the machine vision system.
Thus, it would be desirable to have a system and method capable of estimating the remaining useable life of a contactor and impending faults thereof. It would also be advantageous if the system and method were customizable by a user to accommodate different application requirements and user preferences.